A fun way to say "man" usually when talking lightheartedly with your buds (mangs). in certain social situations "mang" can be quite addictive to use but it seems impossible to overuse it. Also made famous in the muddy waters song "mannish boy".

Hey, wassup mang? I have no idea what you are saying to me or even talking about, mang. I think I need a drink from the liquor store, mang. Your girlfriend is really hot mang. This word can also just be used by itself, such as walking past somebody soluting them and screaming at the top of your lungs "mang."

Plain and simple, this was started by the Mexicans. It's their way of saying "Man".. This is due to the Mexican accent converted to English. Now people say 'mang' because it's (1) different and (2) humorous.